Equivalent base load hours computer



June 23, 1970 w. H. .CROWELL 3,

EQUIVALENT BASE LOAD HOURS COMPUTER Filed Dec. 15, '19s? DRIVER COUNTE Rg? INVENTOR, WILLIAM H. CROWELL ATTORNEY.

United States Patent Otfice 3,517,177 EQUIVALENT BASE LOAD HOURSCOMPUTER William H. Crowell, Lansdale, Pa., assignor to Honeywell Inc.,Minneapolis, Minn., a corporation of Delaware Filed Dec. 15, 1967, Ser.No. 690,891 Int. Cl. G06g 7/18; 7/64; G011 3/00 US. Cl. 235183 8 ClaimsABSTRACT OF THE DISCLOSURE It is well known that most prime movers havedeterminable useful operating lives. The useful operating life isdefined as the life during which the prime mover may operate prior toeither breakdown or maintenance. The useful operating life is a functionof many variables of the physical system. For example, the output loaddriven and/ or produced by the prime mover, the temperature of thephysical system, the pressure relative to the physical system and thelike are typical variables of a physical system. The useful operatinglife of such a prime mover is established as a number of hours ofoperation under a set of standard or optimized conditions and isidentified as the Base Load of the machine. It is axiomatic that themachine will not always be operated at the Base Load condition. Avariation from any or several of the standard conditions produces acalculable variation in the number of hours of the useful operating lifeof the machine. Such a shift in the useful operating life is identifiedas the Equivalent Base Load Hours. Accordingly, these variables may beoperated upon individually or together to produce a mathematicalexpression of the operating life of the prime mover.

Because of the last mentioned relationship, it--is desirable to be ableto compute the consumption or the rate of consumption of the useful lifeof the prime mover under operating conditions. This information is usedso that the prime mover is not overloaded or excessively operated underundesirable conditions. Moreover, the prime mover is not removed fromuseful production and overhauled prior to the actual necessity thereofif the useful life of the prime mover has not been fully utilized.

Therefore, the subject invention relates to a computer which manipulatesinput signals in accordance with a mathematical expression of themeasurable variable such that the rate of consumption of the usefuloperating life of a prime mover can be monitored. In a preferredembodiment, the computer utilizes a plurality of amplifiers forproducing and/or summing the various expressions of constants and/ormeasurable variables, a time division multiplier for producing a signalrepresentative of the equivalent base load on the prime mover, timeintegration means for selectively operating upo the rate signals toproduce an indication of the percentage of operating life which has beenconsumed. In addition, a switching circuit is utilized to selectivelyinclude a simulated base load signal if the actual operational load isbelow a minimum value.

Consequently, one object of this invention is to provide a base loadcomputing circuit.

Another object of this invention is to provide a computing circuit whichindicates the consumption of useful operating life of a prime mover.

Another object of this invention is to provide a com- 3,517,177 PatentedJune 23, 1970 puting circuit wherein the operation of a prime mover isdetected and rated for purposes such as billing or maintenance or thelike.

These and other objects and advantages of this invention will becomemore readily apparent when the following description is read inconjunction with the single figure which is a schematic diagram of thecomputing circuit.

Referring now to the drawing, the schematic diagram includes amplifiers1, 2 and 3 which are connected as linear amplifiers having apredetermined loop gain. In addition, amplifier 4 is connected as anintegrating amplifier while amplifier Sis connected as a comparator.

More specifically, variable resistor 10 is connected between a +15 voltsource and ground. The variable tap of resistor 10 is connected viafixed resistor 11 and variable resistor 12 to the input of amplifier 1.Variable resistor 12 is connected such that the resistance thereof inseries with resistor 11, may be varied. The output of amplifier 1 isconnected via normally open contacts K2B and resistor 14 to the input ofamplifier 1. Normally closed contacts K2A and temperature sensitiveresistor 13 are also connected between the output and the input ofamplifier 1.

The coil K2 associated with contacts K2A and K2B are connected to switch40- and source 39. Thus, by closing switch 40 during the calibrationoperation, coil K2 is energized. When energized, coil K2 causes contactsK2A to open and contacts K2B to close. It should be noted that resistor14 is a precision resistor which is equal to the resistance oftemperature sensitive resistor 13 at a predetermined temperature.Therefore, when in the calibration mode, resistor 12 is varied such thatthe loop gain of amplifier 1 is unity. That is, resistor 12 is set equalto the resistance of resistor 14 whereby unity gain of amplifier 1 atthe predetermined base temperature is achieved.

Resistor 13, a temperature sensitive resistor, may be a high precisionnickel probe. This type of probe exhibits extreme sensitivity andaccuracy in measuring temperature. Since it is frequently desirable tomeasure the temperature of a physical system relating to a prime moverat a fixed predetermined temperature, the resistance value of the probeat the predetermined temperature is calculated and used duringcalibration. The output of amplifier 1 is connected via couplingresistor 15 to summing junction 37 at the input of amplifier 3.

Variable resistor 17 is connected between a +15 volt source and ground.The variable tap of resistor 17 is connected via resistor 16, to summingjunction 37. Resistors 16 and 17 provide an input signal which is aconstant which is utilized to represent a characteristic of a particularprime mover. This constant may vary between different prime movers. Aswell, the constant may vary in relation to the type of measurablevariable of the physical system which provides other inputs.

Another measurable variable is supplied at terminal 41 Where thismeasurable variable represents a signal which is referred to groundpotential. This signal may represent, for example, pressure of thephysical system or the power generated by the prime mover or the like.Terminal 41 is connected to the input of amplifier 2 via variableresistor 21 and fixed resistor 22. The output of amplifier 2 isconnected to the input thereof via feedback resistor 23. Resistors 22and 23 are designed to produce a suitable loop gain of amplifier 2, forexample 60, to operate upon the signal applied at terminal 41. However,inasmuch as the desired output signal of amplifier 2 is a function ofother environmental conditions such as atmospheric pressure and thelike, as well as the input signal at terminal 41, resistor 21 isinserted to provide variability in the amplifier loop gain. Typically,variable resistor 21 is set at the predetermined initial conditions andthereafter said resistor is used to adjust the gain of amplifier 2. Asthe system variable represented by resistor 21 is varied, resistor 21 isalso varied to insert a larger resistance into the equation-representingamplifier 2 such that the gain thereof is decreased. The output ofamplifier 2 is connected via resistor 24 to summing junction 37.

Summing junction 37 is connected to an input of amplifier 3. Thefeedback network connected around amplifier 3 includes resistor 18 andswitch 20. In addition, depending upon the position of switch 20, thefeedback network may be connected either directly or via resistor 19 tothe output of amplifier 3. When amplifier 3 is connected to the feedbacknetwork as shown, the loop gain thereof is typically unity. However, inthe event that the loop gain of 60 is too large for amplifier 2 andproduce instability or other inaccuracy, amplifier 3 may be designed tohave a loop gain of 2 while amplifier 2 has a loop gain of 30. In thefeedback condition shown, the output signal Z of amplifier 3 is afunction of the signals which are supplied to summing junction 37. Ifswitch 20 is repositioned, to insert resistor 19 in the feedbackcircuit, the output signal Z is a function of the signals supplied atsumming junction 37 modified by a factor represented by resistor 19. Itshould be noted that the factor represented by resistor 19 is correlatedwith the signal effect produced by resistor 21.

The signal Z produced by amplifier 3 is supplied to an input of the timedivision multiplier TDM 25. A suitable circuit for performing thisfunction is shown in the copending application of W. H. Crowell, theinstant inventor, entitled Time Division Multilier, bearing Ser. No.675,596, filed Oct. 16, 1967 and assigned to the common assignee. In thereferenced patent application, there is disclosed an arithmetic circuitwhich includes a plurality of operational amplifiers interconnected tooperate upon an input signal in such a manner that, inter alia, areciprocal function is provided. The time division multiplier describedin the copending application is not a part of this invention, per se,but is a preferred means for supplying the reciprocal signal l/Z at theoutput thereof.

The output signal supplied by TDM is supplied via normally closedcontacts KIA to the armature of switch 38. Depending upon the positionof switch 38, the signal is supplied to the input of integratingamplifier 4 via resistor 27 either directly or via variable resistor 26.It should be noted that switches 38 and 20 are ganged and operatetogether. The switches are concurrently in the position shown. In thealternative, both switches are in the opposite position. Thus, it willbe seen that when resistor 19 is connected in the feedback circuit ofamplifier 3, resistor 26 is disconnected from the input circuit ofamplifier 4. In other words, if the factor represented by resistance 19is inserted into the signal Z, it is not necessary to insert it into thesignal 1/Z. Conversely, if the signal Z does not include the resistance19 factor, a corresponding similar factor is inserted into the 1/ Zsignal by means of resistor 26.

The output of amplifier 4 is connected to the input thereof viaintegrating capacitor 28. The output of amplifier 4 is further connectedto a counter driver 29. The output of counter driver 29 is supplied to asuitable counter 30 wherein a digital output is presented and/ordisplayed.

Thus, it is seen that amplifier 4 integrates the signal l/Z as afunction of time and provides a suitable output signal. In a preferredembodiment, the time constant for the inegrator amplifier 4 may be onthe order of hour or 6 minutes. On the other hand, the counter 30 may bedesigned to provide an indication which is related to hours. In thiscase, a decade counter or divider maybe inserted before the counter.Obviously, if the time constant of amplifier 4 is enlarged and thecounting rate of counter 30 is reduced, the decade counter may beeliminated or, conversely, expanded to provide a greater number ofcounts if desired.

Thus, it is seen that this computer circuit operates upon at least fourfactors, two of which are representative of measurable variable of aphysical system, one of which is a constant which is a function of thephysical system and one of which is a function of its environment. Theseinput signals are vectorially or algebracically summed to produce anoutput signal Z which is repreentative of the continuously computed,instantaneous useful life of the prime mover. The instantaneous lifeexpectancy signal is converted into a rate of consumption signal whichis integrated to produce a percentage or similar satisfactory outputsignal representative of the actual useful life consumption.

As an additional feature, the output signal produced by TDM 25 may beconnected via resistor 34 to an input of amplifier 5. A variableresistor 32 is connected between a l5 volt source and ground. Thevariable tap of resistor 32 is connected via fixed resistor 33 to input36 of amplifier 5. Thus, the low level setpoint signal provided at thevariable tap of resistor 32 is subtracted from the output signal ofTDM25 at the summing junc tion 36. Zener diode 35 is connected in afeedback path around amplifier 5. Specifically, the anode of Zener diode35 is connected to summing junction 36 while the cathode of Zener diode35 is connected to the output of amplifier 5 along with coil K1 which isreferenced to ground. With this configuration, amplifier 5 operates as acomparator which produces a low level signal when the signal 1/ Z fromTDM25 is greater than the low level set oint signal supplied viaresistor 33. However, when the signal at summing junction 36 assumes anegative level, amplifier 5 produces a high level output signal whichenergizes coil K1. When coil K1 is energized, contacts KIA are openedand contacts KlB are closed. Thus, the input of amplifier 4 is connectedto the variable tap of resistor 31 which is connected between a +15 voltsource and ground, instead of to the output of TDM25. This connectionhas the effect of supplying a constant signal of a predetermined levelto the input of amplifier 4 whereby the amplifier 4 continues tointegrate this predetermined signal and produce an output at counter 30.In essence, this operation has the effect of continuing the calculationof the consumption of the operating life at a minimum level, even thoughthe actual consumption level may be less than the minimum level. Thus, acertain safety factor is built into the system. In the event that thesystem is used as a billing or metering system, this has the efifect ofestablishing a base minimum billing rate regardless of relatively lowutilization of the prime mover.

Thus, the preferred embodiment of an equivalent base load measuringsystem has been described. This system operates upon suitable measurablevariables produced by the prime mover or other systems being monitored.It is clear that modifications of this system will be suggested to thoseskilled in the art. Any modifications of this system which fall withinthe inventive precepts supra, are meant to be included in thisdescription.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A computer for computing the equivalent base load hours of a primemover comprising, in combination, first input means including means forderiving a signal representative of a first significant parameterdeterminative of said equivalent base load hours and including a firstamplifier means for generating a first signal,

second input means to which signals representative of a secondsignificant parameter determinative of said equivalent base load hoursmay be applied, second amplifier means, said second input means beingconnected for supplying signals to said second amplifier means forgenerating a second signal,

means for establishing a signal representative of the base loadcharacteristic of said prime mover,

arithmetic means for algebraically adding said three recited signals toproduce a composite signal which is a function of the equivalent baseload of the prime mover, and integrating means connected to integrate afunction of said composite signal to produce a signal representative ofsaid equivalent base load hours of said prime mover.

2. The combination recited in claim 1 wherein said first input meansincludes temperature sensitive means, said temperature means beingconnected in the feedback path of said first amplifier means.

3. The combination recited in claim 1 'wherein said second input meansincludes compensating means, said compensating means providingadjustment for environmental conditions relative to a physical systemrelated to said combination.

4. The combination recited in claim 1 wherein said arithmetic meansincludes a third, or summing amplifier for summing and weighting saidthree recited signals.

5. The combination recited in claim 4 wherein said arithmetic meansincludes means connected to the output of said summing amplifier forproviding a signal representative of the reciprocal of the output signalof said summing amplifier, said integrating means being connected tointegrate said reciprocal signal.

6. The combination received in claim 5 including comparator meansconnected to said arithmetic means, simulated input means, saidcomparator producing a control 6 signal as a function of the outputsignal produced by said arithmetic means, and switch means controlled bysaid control signal produced by said comparator means, said switch meansselectively connecting said integrating means to said simulated inputmeans or the output of said arithmetic means.

7. The invention set forth in claim 5 including the addition of digitaloutput means for displaying an output signal.

8. The combination recited in claim 4 including compensating meansconnected in the feedback path of said third amplifier means to provideadjustment for environmental conditions relative to the prime mover.

References Cited UNITED STATES PATENTS 2,946,943 7/1960 Nye et al.235--183 X 3,237,448 3/1966 Howell et a1 235183 X 3,250,901 5/1966 Brahm235183 2,357,239 12/1967 Hohenberg 235183 X 3,362,217 1/1968 Evans et al235-183 X EUGENE G. BOTZ, Primary Examiner F. D. GRUBER, AssistantExaminer US. Cl. X.R.

